Abstract
A microfluidic biosensor is proposed using a microwave substrate-integrated waveguide (SIW) cavity resonator. The main objectives of this noninvasive biosensor are to detect and analyze biomaterial using tiny liquid volumes (3 μL). The sensing mechanism of our proposed biosensor relies on the dielectric perturbation phenomenon of biomaterial under test, which causes a change in resonance frequency and return loss (amplitude). First, an SIW cavity is realized on a Rogers RT/Duroid 5870 substrate. Then, a microwell made from polydimethylsiloxane (PDMS) material is loaded on the SIW cavity to observe the perturbation phenomenon. The microwell is filled with phosphate-buffered saline (PBS) solution (reference biological medium). To demonstrate the sensing behavior, the fibroblast (FB) cells from the lungs of a human male subject are analyzed and one-port S-parameters are measured. The resonance frequency of the structure with FB cells is observed to be 13.48 GHz. The reproducibility and repeatability of our proposed biosensor are successfully demonstrated through full-wave simulations and measurements. The resonance frequency of the FB-loaded microwell showed a shift of 170 MHz and 20 MHz, when compared to those of empty and PBS-loaded microwells. Its analytical limit of detection is 213 cells/μL. Our proposed biosensor is noncontact and reliable. Furthermore, it is miniaturized, inexpensive, and fabricated using simple- and easy-design processes.
Highlights
Miniaturized sensors can be integrated with other components/system and can be cost effective, and mass production is an essential step to realize point-of-care testing [1]
A few substrate-integrated waveguide (SIW) cavity resonators have been proposed as chemical sensors, but only one of them has been experimentally demonstrated as a biosensing device [26]
The vertical distribution of the electric field vector (Figure 2(c)) suggests that a cylindrical/cup-shaped microcontainer loaded at the center of the SIW cavity would be the best option because it would allow the maximum electric field lines to pass through the liquid-filled microcontainer that makes the interaction with the electric field lines even more strong
Summary
Miniaturized sensors can be integrated with other components/system and can be cost effective, and mass production is an essential step to realize point-of-care testing [1]. Its planar structure allows straightforward integration of active circuits and passive components It offers a low-cost, compact design with an easy fabrication process. A few SIW cavity resonators have been proposed as chemical sensors, but only one of them has been experimentally demonstrated as a biosensing device [26] They discriminated the alive and dead cells of Chinese hamster ovarian cells using an SIW structure. The novelty of our proposed research is that this is the first time that the detection of fibroblast cells is demonstrated using the SIW cavity-based RF biosensor. Excellent performance and other advantages (e.g., compact design, low cost, and rapid detection) of microwave-assisted microfluidic biosensor, as discussed in the previous paragraphs, make it an attractive choice to detect and analyze the fibroblast cells. The proposed sensor can detect fibroblast (FB) cells using the frequency shift in the microfluidically loaded SIW cavity. The performance of the proposed sensor is demonstrated through full-wave simulations and S-parameter measurements
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